Thomas W. Polger

Realization and the metaphysics of mind1

According to a familiar view in philosophy of mind, mental states or properties are realized by physical states or properties but are not identical to them. This view is often called realization physicalism. But what is realization? I argue that recent approaches to realization, represented by Carl Gilletts ‘dimensioned’ view, fail to acknowledge some textbook cases of realization. I also argue Gilletts account in particular admits realization relations that should not count if realization physicalism is to be distinguished from its competitors in the usual ways. I offer my own account of realization, and argue that it is superior not only in passing the above tests but also in its utility for answering questions about multiple realizability.

Evaluating the evidence for multiple realization

AbstractConsider what the brain-state theorist has to do to make good his claims. He has to specify a physical–chemical state such that any organism (not just a mammal) is in pain if and only if (a) it possesses a brain of suitable physical–chemical structure; and (b) its brain is in that physical–chemical state. This means that the physical–chemical state in question must be a possible state of a mammalian brain, a reptilian brain, a mollusc’s brain (octopuses are mollusca, and certainly feel pain), etc. At the same time, it must not be a possible (physically possible) state of the brain of any physically possible creature that cannot feel pain. Even if such a state can be found, it must be nomologically certain that it will also be a state of the brain of any extraterrestrial life that may be found that will be capable of feeling pain before we can even entertain the supposition that it may be pain.It is not altogether impossible that such a state will be found... . But this is certainly an ambitious hypothesis. (Putnam 1967/1975, p. 436) The belief that mental states are multiply realized is now nearly universal among philosophers, as is the belief that this fact decisively refutes the identity theory. I argue that the empirical support for multiple realization does not justify the confidence that has been placed in it. In order for multiple realization of mental states to be an objection to the identity theory, the neurological differences among pains, for example, must be such as to guarantee that they are of distinct neurological kinds. But the phenomena traditionally cited do not provide evidence of that sort of variation. In particular, examples of neural plasticity do not provide such evidence.

Putnam's Intuition

Multiple realizability has recently attractedrenewed attention, for example Bickle, 1998;Bechtel and Mundale, 1999; Bechtel and McCauley,1999; Heil, 1999; and Sober, 1999. Many of thesewriters revisit the topic of multiplerealizability in order to show that someversion of a mind-brain identity theory isviable. Although there is much of value inthese recent explorations, they do not addressthe underlying intuitions that have vexedphilosophers of mind since Hilary Putnamintroduced the concern (1967). I argue that thestandard way of construing multiplerealizability is a much stronger claim thanthat of Putnams intuition alone. I distinguishfour interpretations of the multiplerealizability intuition. Some commonformulations of multiple realizability arealmost certainly true, while others are not atall plausible. I argue that the plausible formsof multiple realizability do not impugn theprospects for a mind-brain Identity Theory.

Are sensations still brain processes

Fifty years ago J. J. C. Smart published his pioneering paper, “Sensations and Brain Processes.” It is appropriate to mark the golden anniversary of Smarts publication by considering how well his article has stood up, and how well the identity theory itself has fared. In this paper I first revisit Smarts (1959) text, reflecting on how it has weathered the years. Then I consider the status of the identity theory in current philosophical thinking, taking into account the objections and replies that Smart discussed as well as some that he did not anticipate. Finally, I offer a brief manifesto for the identity theory, providing a small list of the claims that I believe the contemporary identity theorist should accept. As it turns out, these are more or less the ones that Smart defended fifty years ago.

Two Confusions Concerning Multiple Realization

Despite some recent advances, multiple realization remains a largely misunderstood thesis. Consider the dispute between Lawrence Shapiro and Carl Gillett over the application of Shapiro’s recipe for deciding when we have genuine cases of multiple realization. I argue that Gillett follows many philosophers in mistakenly supposing that multiple realization is absolute and transitive. Both of these are problematic. They are tempting only when we extract the question of multiple realization from the explanatory context in which it is invoked. Anchoring multiple realizability in its theoretical context provides grounds for arbitrating disagreements. Doing so, I argue, favors the view advanced by Shapiro.

Identity, variability, and multiple realization in the special sciences

Compositional variation and variability in nature is abundant. This fact is often thought to entail that multiple realization is also ubiquitous. In particular, compositional variability among cognitive creatures is thought to provide conclusive evidence against the mind-brain type identity theory. In this chapter we argue that the type identity theory, properly understood, is compatible with a wide range of compositional and constitutional variation and variability. Similarly, contrary to received wisdom, variation poses no threat to reductionist ventures. Multiple realization as we understand it, requires a specific pattern of variation. Multiple realization is not self-contradictory; the kinds of variation that qualify as multiple realization are not impossible, but they are less common in general than is widely supposed.

Neural Machinery and Realization

The view that the relationship between minds and brains can be thought of on the model of software and hardware is pervasive. The most common versions of the view, known as functionalism in philosophy of mind, hold that minds are realized by brains. The question arises, What is the realization relation? I approach the question of realization through a case study: David Marr’s (1982) computational account of early visual processing. Marr’s work is instructive because it is the textbook case of the hierarchy of mechanisms that has seemed to bear out the arguments of functionalist philosophers and cognitive scientists. I argue that realization as employed by Marr has some but not all of the characteristics that it is usually taken to have.

Mechanisms and explanatory realization relations

My topic is the confluence of two recently active philosophical research programs. One research program concerns the metaphysics of realization. The other research program concerns scientific explanation in terms of mechanisms. In this paper I introduce a distinction between descriptive and explanatory approaches to realization. I then use this distinction to argue that a well-known account of realization, due to Carl Gillett, is incompatible with a well-known account of mechanistic explanation, due to Peter Machamer, Lindley Darden, and Carl Craver (MDC, Philos Sci 57:1–25, 2000). This is surprising, not least of which because Gillett has cited MDC’s work as evidence that his account of realization is the right way to think about realization in the sciences.

Color Vision and the Four-Color-Map Problem

Four different colors are needed to make maps that avoid adjacent countries of the same color. Because the retinal image is two dimensional, like a map, four dimensions of chromatic experience would also be needed to optimally distinguish regions returning spectrally different light to the eye. We therefore suggest that the organization of human color vision according to four-color classes (reds, greens, blues, and yellows) has arisen as a solution to this logical requirement in topology.

Functionalism as a philosophical theory of the cognitive sciences

Functionalism is a philosophical theory (or family of theories) concerning the nature of mental states. According to functionalism psychological/cognitive states are essentially functional states of whole systems. Functionalism characterizes psychological states essentially according to what they do, by their relations to stimulus inputs and behavioral outputs as well as their relations to other psychological and nonpsychological internal states of a system. The central constructive relation for functionalism is the so-called realization relation. Realization is a proposal for how psychological states can be real, physical, and causally efficacious while at the same time preserving the autonomy of cognitive explanations and avoiding reduction or elimination. WIREs Cogn Sci 2012, 3:337-348. doi: 10.1002/wcs.1170 For further resources related to this article, please visit the WIREs website.